This invention is directed to electronic detectors and, more particularly, to electronic detectors for determining which tone of particular set of tones exists in a received or incoming signal, such as a signal of the type generated by a push bottom type telephone.
In various types of electronic systems, it is important to determine which tone of a series of tones exists in an incoming signal. For example, in telephone tone-to-pulse conversion systems adapted to convert dual tone or DMT signals of the type generated by push bottom telephones into rotary dial type pulses, it is necessary to identify the frequencies of a pair of received tones and utilize information about these frequencies to control the generation of rotary dial type pulses. More specifically, when a button of a push button telephone is depressed, a dual tone multifrequency frequency (DTMF) signal is generated. One of the dual tones is a high frequency tone and the other tone is a low frequency tone. It is relatively easy to segregate the high frequency tones from the low frequency tones. However, it is difficult to determine which particular tone of a set of low frequency tones (or a set of high tones) actually exists. Various types of relatively sophisticated electronic circuitry have been developed to determine this information. Such circuits usually include relatively complex signal filters and level detectors, or digital counters and memory systems for determining and verifying this information. Obviously, highly sophisticated electronic systems are expensive to manufacture and produce, whereby the cost of tone-to-pulse conversion is greater than desirable. This invention is directed to overcoming these disadvantages and provide a relatively uncomplicated tone detector suitable for detecting which tone of a particular set of high or low frequency tones actually exists.
Therefore, it is an object of this invention to provide a new and improved tone detector.
It is a further object of this invention to provide a new and improved tone detector suitable for use in tone-to-pulse or tone-to-mark conversion systems.
It is yet another object of this invention to provide a tone detector suitable for use in telephone systems adapted to convert DTMF signals into signal forms required by rotary dial operated signaling or switching systems.